Arrangement for multiple 1xn optical switches

ABSTRACT

A compact arrangement of multiple I1×N optical switches in a single optical switch package is described.

BACKGROUND OF THE INVENTION

[0001] The invention relates to fiber optic switches.

[0002] Typically, in the fabrication of dense N×N switches, two N×Nswitch cores or fabrics are required for redundancy. In each switchcore, a signal emanating from an incoming fiber is split and returnpaths are recombined. Such switching may be implemented with individualswitching mechanisms, which select desired paths. As overall switch coresize (i.e., the value N) continues to increase, so too does the numberof individual switching mechanisms that must be packaged in a singleport unit.

SUMMARY OF THE INVENTION

[0003] In one aspect of the invention, a fiber optic switch assemblyincludes a first strip arrangement of deflecting mirrors and a secondopposing strip arrangement of deflecting mirrors, the deflecting mirrorsin the first and second strip arrangements being configured to operatetogether to form a plurality of switches.

[0004] Embodiments of the invention include one or more of the followingfeatures.

[0005] Ones of the deflecting mirrors in each strip each can receive anoptical beam and provide the optical beam to a selected one of N of thedeflecting mirrors in the opposing strip.

[0006] Among the advantages of the present invention are the following.The interleaving of 1×N switches provides for a very compactarrangement, thus reducing the overall packaging size of a switchassembly. Such a compact arrangement is of particular interest for fiberoptical switching applications that require that many switches bepackaged as a single unit.

[0007] Other features and advantages of the invention will be apparentfrom the following detailed description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is an illustration of a switch configured to include four1×2 switches.

[0009]FIG. 2A is a side view of the switch depicted in FIG. 1.

[0010]FIG. 2B is a top view of the switch depicted in FIG. 1.

[0011]FIGS. 3A and 3B are top and side views, respectively, of anexemplary mirror structure.

[0012]FIG. 4 is an illustration of a detector arrangement to optimizecoupling for each switching path in the switch of FIGS. 1 and 2A-2B.

[0013]FIG. 5 is an illustration of an alternative 1×2 switch arrangementthat uses a latching switch element.

DETAILED DESCRIPTION

[0014] Referring to FIG. 1, a switch 10 includes an arrangement of twoarrays or strips 12 a, 12 b of mirrors 14 a, 14 b, 14 c, 14 d, 14 d, 14e and 14 f, and 16 a, 16 b, 16 c, 16 d, 16 e and 16 f, respectively. Themirrors 14, 16 as described herein are two-dimensional mirrors.Alternatively, the mirrors 14, 16 can be one-dimensional mirrors. Themirrors are grouped to form one input by N outputs (1×N) switches 18,where N has a value of 2. The mirrors 14 a, 14 d, 16 c and 16 f serve asinputs and the other mirrors serve as outputs. The mirrors 14 a, 16 aand 16 b form a first switch 18 a, the mirrors 16 c, 14 b and 14 c forma second switch 18 b, the mirrors 14 d, 16 d and 16 e form a thirdswitch 18 c, and the mirrors 16 f, 14 e and 14 f form a fourth switch 18d. Light directed to the mirror 14 a in the mirror strip 12 a from alaunching collimator (not shown) is directed by the mirror 14 a towardseither of the target mirrors 16 a or 16 b in the opposing mirror strip12 b. Light falling on the mirror 16 c in the mirror strip 12 b isdirected towards either the mirror 14 b or the mirror 14 c in the mirrorstrip 12 a. Likewise, the mirror 14 d directs a light beam to a selectedone of the target mirrors 16 c and 16 d, and the mirror 16 f directs alight beam to a selected one of the target mirrors 14 e and 14 f. It canbe seen from the figure that the switches 18 a and 18 c have oneorientation and the switches 18 b and 18 d have a second orientationthat is the opposite of the first orientation. For a compact arrangementof switches as shown, therefore, the switches having the firstorientation are interleaved with the switches having the secondorientation. That is, the inputs, 14 a, 14 d, 16 c and 16 f of theswitches 18 a, 18 c, 18 b and 18 d, respectively, are oriented foralignment with outputs of adjacent ones of the switches 18. For example,the input 14 a of the switch 18 is in line with the outputs 14 b and 14d of adjacent switch 18 b, and, likewise, the input 16 c of the switch18 b is in line with the outputs 16 a, 16 b of the switch 18 a, as wellas the outputs 16 de and 16 e of the switch 18 c, also adjacent to theswitch 18 b.

[0015] Since the target mirrors, e.g., 14 e and 14 f, are closetogether, the deflection angles for the mirror from which the beam isdeflected (for the example of target mirrors 14 e, 14 f, that mirrorwould be the mirror 16 f) can be quite small and the driving voltagesrequired for deflection are also very small. For example, if thedistance from lens to lens is 50 mm (using a 1.5 mm focal length lens),and the mirror spacing is 1 mm, then the required mirror deflection isonly a little more than half a degree. The deflection angle can befurther reduced by orienting the beam launching collimator for each 1×2switch such that the undeflected target position is half way between thetwo target mirrors, again reducing the angle that needs to be used. Onlyone deflection direction along the strip needs appreciable deflection.The other direction requires only a very small correction, if themechanical alignment is done correctly. Of course, and as indicatedabove, the mirrors could be one-dimensional and therefore deflect in onedirection only.

[0016] Referring to FIGS. 2A and 2B, an assembly for the switch 10 (ofFIG. 1), switch assembly 20, includes two assemblies 22 and 24, whichare tightly clamped together with pin 26. Assembly 24 is a monolithicblock which holds lenses 28, 28′ and fiber with fiber ferrules 30 a, 30b, which are adjusted against each other to produce maximum throw of thewaist coming out of the fiber at the end of the ferrules 30 a, 30 b. Theassembly 22 holds the mirror strips 12 a and 12 b (that includeassociated substrates, e.g., silicon, ceramic, glass, etc.), which haveconnecting ribbons 32 a and 32 b for their leads. The assembly 20further includes heaters 34 and a temperature sensor 36 to provide astabilized thermal environment. The switch assembly 20 may be thermallyisolated from its environment with an insulated jacket (notillustrated).

[0017] With reference to FIGS. 3A-3B, an exemplary mirror stripstructure 40 for implementing the mirror strips 12 a, 12 b is shown inpartial view. The mirror strip structure 40 includes micro-mirrorstructures 42 (which correspond to the mirrors 14, 16 in FIG. 1), eachof the micro-mirror structures 42 including a mirror arrangement 44disposed above and supported over a top surface of a reference member orsubstrate 46. To illustrate the detail of the mirror structures 42, onlythree are shown in the figure. It will be appreciated that there wouldbe six micro-mirror structures 42 in each of the strips 12 a, 12 b inthe switch 10 of FIG. 1. As shown in FIG. 3A, each mirror arrangement 44includes a mirror 48 coupled to mirror frame 50 by a first pair oftorsion members 52 a, 52 b. The mirror arrangement 44 further includes asecond pair of torsion members 54 a, 54 b, which couple the mirror frame50 to strips 56.

[0018] Referring to FIG. 3B, the substrate 46 includes a base portion58, a raised portion 60 on the base portion 58, and sidewall portions 62on either side of the base portion 58. The substrate may be made ofceramic or other suitable materials. The strips 56 are located on top ofthe sidewalls 62. As shown by the raised portion 60 (FIG. 3A), theraised portion 60 is conical or quasi-conical in shape.

[0019] Electrodes 64 are disposed on the surface of the raised portion60 to impart a rotational motion to the mirror 48 and the mirror frame50 (shown in FIG. 3A). The electrodes 64 control the inner rotation ofthe mirror arrangement around the torsion members 52 a, 52 b (“x-axis”),as well as control the outer rotation of the mirror arrangement aroundthe torsion members 54 a, 54 b (“y-axis”).

[0020] Preferably, for large deflection angles and small drivingvoltages, the mirror structure includes the raised portion 60 asdescribed and, although the raised portion 60 has been thus described ashaving a cone or cone-like form, it may take any shape or structure thatallows the electrodes 64 to be positioned close to the mirrorarrangement 44 and support rotational movement of the mirror arrangementin the x-y plane. It will be understood, however, that, although theraised portion may be desirable, any other electrode structure orstructure for supporting electrodes can be used. For example, planarelectrodes can be used.

[0021] Preferably, the mirror arrangement 14 and the electrodes 34 areso positioned relative to the cone 30 such that the cone 30 is centeredapproximately under the mirror 18. Substrate areas beneath the mirrorframe 20 need not be conical, but may be sloped on such an angle asrequired to allow the mirror arrangement 14 to rotate freely through itsouter axis of rotation around torsion members 24 a, 24 b. Thesesubstrate areas can be machined linearly in the substrate 16, thussimplifying the fabrication of the substrate 16.

[0022] As can be seen in FIG. 3B, a spacer 65 can be used between eachof the strips 56 and the sidewall portions 62 of the substrate 46 belowsuch strips 56. The angles in the bottom of the substrate 12 are notcritical. Typically, because the substrate 16 is made in sections of4.5″×4.5″, the sections are all made together. The substrate materialmay be machined in vertical and horizontal directions to remove materialunder a desired angle. The cone or cone-like shape is ground on the topto complete the substrate structure or can be etched into the substratesurface. Alternatively, a mold may be made to cast the substratematerial in a green state. In yet another alternative, the electrodescan be plated onto the substrate surface.

[0023] The mirror structure 42 can be fabricated usingsilicon-on-insulator fabrication techniques, with the mirror arrangement44 being defined in the top (or device) silicon wafer. Other fabricationtechniques may be used.

[0024] The embodiment of the mirror structure 42 illustrated in FIGS.3A-3B and various associated fabrication techniques are described morefully in co-pending U.S. patent application, entitled “Improvements foran Optical N×N Switch”, filed on Nov. 16, 2000, incorporated herein byreference.

[0025] Other structures (such as mirror structures having differentelectrode structures, as mentioned above) may be used. For example, themirror strips 12 a, 12 b, and their associated mirror structures 14, 16,respectively, may be constructed in accordance with the techniquesdescribed in U.S. Pat. Nos. 6,044,705 and 5,629,790, incorporated hereinby reference. Other known two-dimensional micro-machined mirrorstructures may be used.

[0026] The deflection of mirrors 14, 16 can be driven by a closed loopsystem. If desired, angle deflection sensors may be used to controldeflection, as described in the above-mentioned application and patents.The deflection may be electrostatic or magnetic or both, in eitherdirection. For example, the axis having the relatively large deflectionmay be magnetic and the relatively smaller deflection axis could beelectrostatic, since the latter requires only minor correction. Thus,even if the mirrors are spaced far apart from each other, there islittle possibility of electrostatic instability.

[0027] Alternatively, the deflectors may be driven open loop, or anexternal alignment scheme may be used. For example, and referring toFIG. 4, a fiber 70 exiting the collimator 30 b (from FIG. 2A) is bent,possibly around a mandrel 71, and produces radiation which is collectedand imaged on a detector 72 with a simple lens (e.g., plastic) orFresnel lens 74. By dithering the driving voltages or currents of thedeflecting mirrors through very small angles and detecting with phasesensitive detection a maximum value for the transmitted power peak(using the detector 72), the mirrors 14, 16 can be locked into anoptimum deflection position for transmission of light from one fiber toanother.

[0028] Although the interleaving scheme is described above withreference to 1×2 switches, it is equally applicable to switches of anysize 1×N, where N is a value of two or greater. Additionally, althoughthe switch 10 is depicted as having four 1×N (where N=2) switches, theswitch 10 could include more or less than the four 1×N switches that areshown.

[0029] The switches 18 have been thus described as having a single inputand N outputs. Alternatively, the switches 18 may have N inputs and oneoutput, or may be operated in two modes so that the mirrors serving asinputs and mirrors serving as outputs in one mode serve as outputs andinputs, respectively, in a second mode. For example, and again referringto FIG. 1, the switches 18 can be operated to use the mirrors 14 b-14 c,14 e, 14 f, 16 a, 16 b, 16 d, 16 e as inputs and the mirrors 14 a, 14 d,16 c and 16 f as outputs. Thus, each of the 1×2 switches could have twoinputs and one output and thus select one of the input signals (that is,the optical beams) received at a corresponding one of the two inputmirrors to be directed to the single output mirror.

[0030] Other embodiments of a 1×2 switch for use in a switch including aplurality of 1×2 switches, such as the switch 10, are contemplated. Forexample, and referring to FIG. 5, a 1×2 switch can be implemented with asingle latching switch element 82 arranged in a configuration withcollimator and fiber assemblies (hereinafter, collimators) 84 a-84 c,shown as switch 80. The collimator 84 a serves a launching collimatorand the collimators 84 b and 84 c serve as exiting collimators. Each ofthe collimators 84 is coupled to one or the other of the mirror strips12 a, 12 b, and are preferably situated in “V” shaped grooves in thesilicon substrate. The latching switch element 82 may be implementedwith magnetic actuating and electrostatic clamping, as described inco-pending U.S. patent application Ser. No. 09/388,772, incorporatedherein by reference.

[0031] The operation of the switch 80 is as follows. When the latchingswitch element 82 is not activated, the optical beam path is from thecollimator 84 a to the collimator 84 b. When the latching switch element82 is activated (by electrostatic clamping) for positioning at a 45degree angle as shown, a beam from the collimator 84 a is directed notto the collimator 84 b but instead to the collimator 84 c. Although thelatching switch element 82 is clamped electrostatically in a particularposition, minor adjustments in the position can still be made, asdescribed in the above-referenced U.S. patent application Ser. No.09/388,772. The mechanical location of the latching switch element 82relative to the collimators 84 can vary, as the associated mirror may betilted and adjusted appropriately in two directions when switching isperformed.

OTHER EMBODIMENTS

[0032] It is to be understood that while the invention has beendescribed in conjunction with the detailed description thereof, theforegoing description is intended to illustrate and not limit the scopeof the invention, which is defined by the scope of the appended claims.Other embodiments are within the scope of the following claims.

What is claimed is:
 1. A fiber optic switch, comprising: a plurality ofswitches, each having one input and N outputs, the switches are arrangedand oriented relative to each other so that the input of a switch is inline with the outputs of any adjacent switches of the plurality ofswitches.
 2. The fiber optic switch of claim 1, wherein the arrangementand orientation of the switches results in a compact arrangement of theplurality of switches.
 3. The fiber optic switch of claim 1, whereineach switch comprises deflecting mirrors configured to form switchingpaths.
 4. The fiber optic switch of claim 3, wherein each deflectingmirror is locked in an optimum deflection angle based on a power peakdetection value determined at a fiber receiving light from such mirror.5. The fiber optic switch of claim 3, wherein the deflecting mirrorsinclude a mirror suspended above a substrate and driving devicesdisposed in the substrate for causing the mirror to rotate in two axesof direction.
 6. A fiber optic switch assembly, comprising: a firststrip arrangement of deflecting mirrors; a second opposing striparrangement of deflecting mirrors; and wherein the deflecting mirrors inthe first and second strip arrangements are configured to operatetogether to form a plurality of switches.
 7. The fiber optic switchassembly of claim 6, wherein the first strip arrangement comprises atleast two inputs spaced apart by at least a pair of outputs and thesecond strip arrangement comprises at least two pairs of outputs spacedapart by an input.
 8. The fiber optic switch assembly of claim 6,wherein ones of the deflecting mirrors in each strip each receive anoptical beam and provide the optical beam to a selected one of N of thedeflecting mirrors in the opposing strip.
 9. The fiber optic switchassembly of claim 6, wherein each deflecting mirror is locked in anoptimum position based on a power peak detection value determined at afiber receiving light from such mirror.
 10. The fiber optic switchassembly of claim 6, wherein each deflecting mirror comprises astructure including a mirror suspended above a substrate and drivingdevices disposed in the substrate for causing the mirror to rotate intwo axes of direction.
 11. A fiber optic switch arrangement comprising:a plurality of mirrors arranged to form switching paths between onemirror in the plurality of mirrors and N other mirrors in the pluralityof; and wherein, in a first mode of operation, the one mirror serves asan input and the N other mirrors serve as outputs such that the onemirror directs an optical beam to the N other mirrors and, in a secondmode of operation, the one mirror serves as an output and the N othermirrors server as inputs such that the one mirror receives an opticalbeam from one of the N other mirrors.
 12. A fiber optic switcharrangement comprising: three collimators, one serving as a launchingcollimator and others serving as exit collimators; a latching switchelement having first and second positions, an optical beam emanatingfrom the launching collimator being directed directly to a first one ofthe exit collimators when the latching element is in the first position,and optical beam emanating from the launching collimator being deflectedby the latching switch element to a second one of the exit collimatorswhen the latching switch element is in the second position.